The present invention relates to electroluminescent filaments ("EL filaments"). More specifically, the present invention relates to EL filaments, portions of which may be individually illuminated.
EL filaments have been known generally in the art; however, few have been produced beyond a test scale and the conventional filaments have had a series of problems, including low reliability and low light intensity. In addition, the conventional EL filaments lack sufficient flexibility to be made into one-, two-, and three-dimensional light emitting objects using textile fabrication technologies such as knitting, weaving, braiding, etc., that use raw materials in filamentary form.
Conventionally, EL filaments include a central solid core conductor coated with a luminescent material and an outer electrode that is made of either a single conductor wound around the core or a transparent conducting film coated onto the luminescing layer. Since the conventional filaments include only a single outer electrode or transparent coated electrode, it is not possible to energize individual portions of the conventional filaments. This is a drawback in applications which require different portions of the filament to be energized at different times; for example, applications that require animated visual effects. The conventional filaments that contain only one outer electrode have the additional drawback that if the outer electrode is broken anywhere along the filament, the whole filament ceases luminescing. This makes the conventional filaments easily susceptible to damage.
There therefore exists a need for a reliable, flexible EL filament that is capable of emitting high light intensity when energized and which may be made into articles or incorporated into articles using textile fabrication techniques. There is also a need for an EL filament, only portions of which may be energized at any one time. Moreover, there is a need for an EL filament which does not fail completely when only a part of the filament is damaged.